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Zebrafish provide a sensitive model of persisting neurobehavioral effects of developmental chlorpyrifos exposure: comparison with nicotine and pilocarpine effects and relationship to dopamine deficits. Neurotoxicol Teratol 2009; 32:99-108. [PMID: 19268529 DOI: 10.1016/j.ntt.2009.02.005] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2008] [Revised: 12/31/2008] [Accepted: 02/13/2009] [Indexed: 11/21/2022]
Abstract
Chlorpyrifos (CPF) an organophosphate pesticide causes persisting behavioral dysfunction in rat models when exposure is during early development. In earlier work zebrafish were used as a complementary model to study mechanisms of CPF-induced neurotoxicity induced during early development. We found that developmental (first five days after fertilization) chlorpyrifos exposure significantly impaired learning in zebrafish. However, this testing was time and labor intensive. In the current study we tested the hypothesis that persisting effects of developmental chlorpyrifos could be detected with a brief automated assessment of startle response and that this behavioral index could be used to help determine the neurobehavioral mechanisms for persisting CPF effects. The swimming activity of adult zebrafish was assessed by a computerized video-tracking device after a sudden tap to the test arena. Ten consecutive trials (1/min) were run to determine startle response and its habituation. Additionally, habituation recovery trials were run at 8, 32 and 128 min after the end of the initial trial set. CPF-exposed fish showed a significantly (p<0.025) greater overall startle response during the 10-trial session compared to controls (group sizes: Control N=40, CPF N=24). During the initial recovery period (8 min) CPF-exposed fish showed a significantly (p<0.01) greater startle response compared to controls. To elucidate the contributions of nicotinic and muscarinic acetylcholine receptors to developmental CPF-mediated effects, the effects of developmental nicotine and pilocarpine exposure throughout the first five days after fertilization were determined. Developmental nicotine and pilocarpine exposure significantly increased startle response, though nicotine (group sizes: Control N=32, 15 mM N=12, 25 mM N=20) was much more potent than pilocarpine (group sizes: Control N=20, 100 microM N=16, 1000 microM N=12). Neither was as potent as CPF for developmental exposure increasing startle response in adulthood. Lastly, developmental CPF exposure decreased dopamine and serotonin levels and increased transmitter turnover in developing zebrafish larvae (N=4 batches of 50 embryos/treatment). Only the decline in dopamine concentrations persisted into adulthood (group sizes: Control N=14, CPF N=13). This study shows that a quick automated test of startle can detect persisting neurobehavioral impairments caused by developmental exposure to CPF. This may be helpful in screening for persisting neurobehavioral defects from a variety of toxicants.
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Assessment of genotoxic and mutagenic effects of chlorpyrifos in freshwater fish Channa punctatus (Bloch) using micronucleus assay and alkaline single-cell gel electrophoresis. Food Chem Toxicol 2009; 47:650-6. [DOI: 10.1016/j.fct.2008.12.021] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2008] [Revised: 11/25/2008] [Accepted: 12/17/2008] [Indexed: 11/23/2022]
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Tait S, Ricceri L, Venerosi A, Maranghi F, Mantovani A, Calamandrei G. Long-term effects on hypothalamic neuropeptides after developmental exposure to chlorpyrifos in mice. ENVIRONMENTAL HEALTH PERSPECTIVES 2009; 117:112-6. [PMID: 19165396 PMCID: PMC2627853 DOI: 10.1289/ehp.11696] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Accepted: 08/22/2008] [Indexed: 05/22/2023]
Abstract
BACKGROUND Increasing evidence from animal and human studies indicates that chlorpyrifos (CPF), similar to other organophosphorus insecticides still widely used, is a developmental neurotoxicant. Developmental exposure to CPF in rodents induces sex-dimorphic behavioral changes at adulthood, including social and agonistic responses, which suggests that CPF may interfere with maturation of neuroendocrine mechanisms. OBJECTIVES We assessed the hypothesis that CPF affects the levels of neurohypophyseal hormones acting as modulators of social behavior in mammals, such as oxytocin (OT), arginine vasopressin (AVP), and prolactin (PRL). METHODS Pregnant female mice were orally administered with either vehicle (peanut oil) or 3 or 6 mg/kg CPF on gestational day (GD) 15 to GD18, and offspring were treated subcutaneously with either vehicle or 1 or 3 mg/kg CPF on postnatal days (PNDs) 11 to PND14. Dose levels were chosen to avoid systemic toxicity and inhibition of brain acetylcholinesterase. Offspring were sacrificed at 5 months of age, and expression of OT, AVP, and PRL was analyzed in the hypothalamus by Western blot or enzyme-linked immunosorbent assay (ELISA) analysis. RESULTS Both male and female mice showed dose-related enhancement of OT expression, with males presenting the more intense effect. AVP expression was significantly reduced in male mice at the higher prenatal and postnatal dose. We observed no significant effect on PRL expression in either sex. Overall, outcomes were mainly attributable to fetal exposure, whereas postnatal doses appeared to potentiate the prenatal effects. CONCLUSIONS Our data indicate that developmental exposure to CPF may permanently interfere with specific key signaling proteins of the hypothalamic peptidergic system, with time-, dose-, and sex-related effects still evident at adulthood.
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Affiliation(s)
- Sabrina Tait
- Section of Food and Veterinary Toxicology, Department of Food Safety and Veterinary Public Health and
| | - Laura Ricceri
- Section of Neurotoxicology and Neuroendocrinology, Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Rome, Italy
| | - Aldina Venerosi
- Section of Neurotoxicology and Neuroendocrinology, Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Rome, Italy
| | - Francesca Maranghi
- Section of Food and Veterinary Toxicology, Department of Food Safety and Veterinary Public Health and
| | - Alberto Mantovani
- Section of Food and Veterinary Toxicology, Department of Food Safety and Veterinary Public Health and
| | - Gemma Calamandrei
- Section of Neurotoxicology and Neuroendocrinology, Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Rome, Italy
- Address correspondence to G. Calamandrei, Section of Neurotoxicology and Neuroendocrinology, Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy. Telephone: 39-06-4990-2106. Fax: 39-06-4957821. E-mail:
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Venerosi A, Cutuli D, Colonnello V, Cardona D, Ricceri L, Calamandrei G. Neonatal exposure to chlorpyrifos affects maternal responses and maternal aggression of female mice in adulthood. Neurotoxicol Teratol 2008; 30:468-74. [DOI: 10.1016/j.ntt.2008.07.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Revised: 07/01/2008] [Accepted: 07/06/2008] [Indexed: 12/20/2022]
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Lassiter TL, MacKillop EA, Ryde IT, Seidler FJ, Slotkin TA. Is fipronil safer than chlorpyrifos? Comparative developmental neurotoxicity modeled in PC12 cells. Brain Res Bull 2008; 78:313-22. [PMID: 18977280 DOI: 10.1016/j.brainresbull.2008.09.020] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2008] [Revised: 09/29/2008] [Accepted: 09/29/2008] [Indexed: 11/28/2022]
Abstract
Fipronil, a GABA(A) receptor antagonist, is replacing many insecticide uses formerly fulfilled by organophosphates like chlorpyrifos. Few studies have addressed the potential for fipronil to produce developmental neurotoxicity. We compared the neurotoxicity of fipronil and chlorpyrifos in undifferentiated and differentiating neuronotypic PC12 cells, evaluating indices of cell replication, cell number, differentiation, and viability for short- and long-term exposures. Fipronil inhibited DNA and protein synthesis in undifferentiated PC12 cells and evoked oxidative stress to a greater extent than did chlorpyrifos, resulting in reduced cell numbers even though cell viability was maintained. In differentiating cells, fipronil displayed an even lower threshold for disruption of development, reducing cell numbers without impairing cell growth, and promoting emergence of neurotransmitter phenotypes; superimposed on this effect, the phenotypic balance was shifted in favor of dopamine as opposed to acetylcholine. Differentiation also enhanced the susceptibility to fipronil-induced oxidative stress, although antioxidant administration failed to provide protection from cell loss. At low concentrations maintained for prolonged periods, fipronil had a biphasic effect on cell numbers, increasing them slightly at low concentrations, implying interference with apoptosis, while nevertheless reducing cell numbers at higher concentrations. Our results suggest that fipronil is inherently a more potent disruptor of neuronal cell development than is chlorpyrifos. The neurodevelopmental effects are not predicated on GABA(A) antagonist properties, since PC12 cells lack the GABA(A) receptor. If fipronil is intended to provide greater safety than chlorpyrifos, then this will have to entail advantages from factors that are yet unexamined: exposure, persistence, pharmacokinetics.
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Affiliation(s)
- T Leon Lassiter
- Department of Pharmacology & Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
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Eaton DL, Daroff RB, Autrup H, Bridges J, Buffler P, Costa LG, Coyle J, McKhann G, Mobley WC, Nadel L, Neubert D, Schulte-Hermann R, Spencer PS. Review of the Toxicology of Chlorpyrifos With an Emphasis on Human Exposure and Neurodevelopment. Crit Rev Toxicol 2008; 38 Suppl 2:1-125. [PMID: 18726789 DOI: 10.1080/10408440802272158] [Citation(s) in RCA: 422] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Eells JB, Brown T. Repeated developmental exposure to chlorpyrifos and methyl parathion causes persistent alterations in nicotinic acetylcholine subunit mRNA expression with chlorpyrifos altering dopamine metabolite levels. Neurotoxicol Teratol 2008; 31:98-103. [PMID: 18977431 DOI: 10.1016/j.ntt.2008.10.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 10/10/2008] [Accepted: 10/14/2008] [Indexed: 10/21/2022]
Abstract
Organophosphates (OPs), commonly used as insecticides, inhibit acetylcholinesterase, the enzyme responsible for the inactivation of synaptic acetylcholine, which results in elevated acetylcholine neurotransmission. Nigrostriatal dopamine neurons receive substantial cholinergic innervation and express a number of nicotinic acetylcholine receptor subunits. Since epidemiological data have implicated pesticides in the incidence of Parkinson's disease, the current experiment investigated how repeated, developmental exposure to the OPs chlorpyrifos (CPS) or methyl parathion (MPT) affects striatal dopamine levels and dopamine neuron gene expression. Newborn rats were treated daily via oral gavage with corn oil vehicle, CPS, or MPT from postnatal days (PND) 1-21. Rats were sacrificed at PND 22 and 50. Levels of dopamine and its metabolites 3,4 dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were measured in the striatum and mRNA expression was measured in the substantia nigra. At 22 days of age, CPS and MPT treatment had no effect on dopamine, DOPAC or HVA levels. At 50 days of age, CPS significantly elevated DOPAC levels and elevated dopamine turnover (DOPAC/dopamine) but did not affect dopamine or HVA levels. MPT had no significant effects on any of these parameters. Interestingly, both CPS and MPT treatments caused a significant alteration in the ratio of alpha7 to alpha6 nicotinic acetylcholine receptor (nAChR) subunit expression in the substantia nigra with a non-significant elevation in alpha6 and a reduction in alpha7 at 22 days. At 50 days of age, a significant elevation in alpha6 nAChR subunit was observed in the MPT treated rats. No differences in dopamine neuron transcription factors (Nurr1 or Lmx1b) or neurotransmission genes were observed. These data demonstrate that repeated exposure to OPs during postnatal maturation can have a significant effect on dopamine neurochemistry, primarily by modifying dopamine metabolism, which can persist for up to 1 month (CPS) and alter acetylcholine subunit expression (CPS and MPT).
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Affiliation(s)
- Jeffrey B Eells
- Center for Environmental Health Sciences, Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, MS 39762, USA.
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Slotkin TA, Bodwell BE, Ryde IT, Levin ED, Seidler FJ. Exposure of neonatal rats to parathion elicits sex-selective impairment of acetylcholine systems in brain regions during adolescence and adulthood. ENVIRONMENTAL HEALTH PERSPECTIVES 2008; 116:1308-14. [PMID: 18941570 PMCID: PMC2569087 DOI: 10.1289/ehp.11451] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2008] [Accepted: 05/19/2008] [Indexed: 05/24/2023]
Abstract
BACKGROUND Organophosphates elicit developmental neurotoxicity through multiple mechanisms other than their shared property as cholinesterase inhibitors. Accordingly, these agents may differ in their effects on specific brain circuits. OBJECTIVES We gave parathion to neonatal rats [postnatal days (PNDs) 1-4], at daily doses of 0.1 or 0.2 mg/kg, spanning the threshold for barely detectable cholinesterase inhibition and systemic effects. METHODS We assessed neurochemical indices related to the function of acetylcholine (ACh) synapses (choline acetyltransferase, presynaptic high-affinity choline transporter, nicotinic cholinergic receptors) in brain regions comprising all the major ACh projections, with determinations carried out from adolescence to adulthood (PNDs 30, 60, and 100). RESULTS Parathion exposure elicited lasting alterations in ACh markers in the frontal/parietal cortex, temporal/occipital cortex, midbrain, hippocampus, and striatum. In cerebrocortical areas, midbrain, and hippocampus, effects in males were generally greater than in females, whereas in the striatum, females were targeted preferentially. Superimposed on this general pattern, the cerebrocortical effects showed a nonmonotonic dose-response relationship, with regression of the defects at the higher parathion dose; this relationship has been seen also after comparable treatments with chlorpyrifos and diazinon and likely represents the involvement of cholinesterase-related actions that mask or offset the effects of lower doses. CONCLUSIONS Neonatal exposure to parathion, at doses straddling the threshold for cholinesterase inhibition, compromises indices of ACh synaptic function in adolescence and adulthood. Differences between the effects of parathion compared with chlorpyrifos or diazinon and the non-monotonic dose-effect relationships reinforce the conclusion that various organophosphates diverge in their effects on neurodevelopment, unrelated to their anticholinesterase actions.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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Slotkin T, Seidler F. Transcriptional profiles reveal similarities and differences in the effects of developmental neurotoxicants on differentiation into neurotransmitter phenotypes in PC12 cells. Brain Res Bull 2008; 78:211-25. [PMID: 18812211 DOI: 10.1016/j.brainresbull.2008.08.021] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Accepted: 08/27/2008] [Indexed: 10/21/2022]
Abstract
Unrelated developmental neurotoxicants nevertheless converge on common functional and behavioral outcomes. We used PC12 cells, a model of neuronal development, to explore similarities and differences for organophosphate pesticides (chlorpyrifos, diazinon), an organochlorine pesticide (dieldrin) and a metal (Ni(2+)), focusing on transcriptional profiles related to differentiation into acetylcholine, dopamine and norepinephrine phenotypes. Agents were introduced at 30 microM for 24 or 72 h, treatments devoid of cytotoxicity. Using microarrays, we examined the mRNAs encoding the proteins involved in neurotransmitter biosynthesis, storage, and degradation, along with the complete panoply of receptors for each transmitter. All three pesticides evoked concordant patterns of effects on genes involved in neural growth and neurite extension, with a distinctly different pattern for Ni(2+). All four toxicants promoted differentiation into the dopamine phenotype at the expense of the acetylcholine phenotype, involving separable effects of each agent on the various gene families; however, there were major differences in the ability of each to promote or repress the norepinephrine phenotype. Chlorpyrifos and diazinon, although displaying many similarities in their transcriptional profiles, also showed major disparities in keeping with their known differences in synaptic and behavioral outcomes after neonatal exposures to these agents in vivo. Surprisingly, there were closer similarities among diazinon, dieldrin and Ni(2+) than for each agent to chlorpyrifos. Our results illustrate how cell culture systems, combined with microarray technology, can screen for developmental neurotoxicants, serving as a model for alternative approaches to the detection and characterization of the impact of exogenous chemicals on brain development.
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Affiliation(s)
- Theodore Slotkin
- Department of Pharmacology & Cancer Biology, Duke University Medical Centre, Durham, NC 27710, USA.
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Carr RL, Nail CA. Effect of different administration paradigms on cholinesterase inhibition following repeated chlorpyrifos exposure in late preweanling rats. Toxicol Sci 2008; 106:186-92. [PMID: 18703558 DOI: 10.1093/toxsci/kfn164] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Chlorpyrifos (CPS) is widely used in agricultural settings and residue analysis has suggested that children in agricultural communities are at risk of exposure. This has resulted in a large amount of literature investigating the potential for CPS-induced developmental neurotoxic effects. Two developmental routes of administration of CPS are orally in corn oil at a rate of 0.5 ml/kg and subcutaneously in dimethyl sulfoxide (DMSO) at a rate of 1.0 ml/kg. For comparison between these methods, rat pups were exposed daily from days 10 to 16 to CPS (5 mg/kg) either orally dissolved in corn oil or subcutaneously dissolved in DMSO, both at rates of either 0.5 or 1.0 ml/kg. A representative vehicle/route group was present for each treatment. Both the low and high volume CPS in DMSO subcutaneous groups were lower than that of the low and high volume CPS in oil oral groups. At 4 h following the final administration, serum carboxylesterase was inhibited > 90% with all treatments. For cholinesterase activity in the cerebellum, medulla-pons, forebrain, and hindbrain, and serum, inhibition in the CPS-oil groups was similar and inhibition in the CPS-DMSO groups was similar. However, significantly greater inhibition was present in the high volume CPS-DMSO group as compared to the CPS-oil groups. Inhibition in the low volume CPS-DMSO group was generally between that in the CPS-oil groups and the high volume CPS-DMSO group. These data suggest that using DMSO as a vehicle for CPS may alter the level of brain ChE inhibition.
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Affiliation(s)
- Russell L Carr
- Center for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi 39762, USA.
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Slotkin TA, MacKillop EA, Melnick RL, Thayer KA, Seidler FJ. Developmental neurotoxicity of perfluorinated chemicals modeled in vitro. ENVIRONMENTAL HEALTH PERSPECTIVES 2008; 116:716-22. [PMID: 18560525 PMCID: PMC2430225 DOI: 10.1289/ehp.11253] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Accepted: 03/03/2008] [Indexed: 05/17/2023]
Abstract
BACKGROUND The widespread detection of perfluoroalkyl acids and their derivatives in wildlife and humans, and their entry into the immature brain, raise increasing concern about whether these agents might be developmental neurotoxicants. OBJECTIVES We evaluated perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorooctane sulfonamide (PFOSA), and perfluorobutane sulfonate (PFBS) in undifferentiated and differentiating PC12 cells, a neuronotypic line used to characterize neurotoxicity. METHODS We assessed inhibition of DNA synthesis, deficits in cell numbers and growth, oxidative stress, reduced cell viability, and shifts in differentiation toward or away from the dopamine (DA) and acetylcholine (ACh) neurotransmitter phenotypes. RESULTS In general, the rank order of adverse effects was PFOSA > PFOS > PFBS approximately PFOA. However, superimposed on this scheme, the various agents differed in their underlying mechanisms and specific outcomes. Notably, PFOS promoted differentiation into the ACh phenotype at the expense of the DA phenotype, PFBS suppressed differentiation of both phenotypes, PFOSA enhanced differentiation of both, and PFOA had little or no effect on phenotypic specification. CONCLUSIONS These findings indicate that all perfluorinated chemicals are not the same in their impact on neurodevelopment and that it is unlikely that there is one simple, shared mechanism by which they all produce their effects. Our results reinforce the potential for in vitro models to aid in the rapid and cost-effective screening for comparative effects among different chemicals in the same class and in relation to known developmental neurotoxicants.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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Slotkin TA, Seidler FJ, Ryde IT, Yanai J. Developmental neurotoxic effects of chlorpyrifos on acetylcholine and serotonin pathways in an avian model. Neurotoxicol Teratol 2008; 30:433-9. [PMID: 18436430 DOI: 10.1016/j.ntt.2008.02.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2008] [Revised: 02/29/2008] [Accepted: 02/29/2008] [Indexed: 11/27/2022]
Abstract
The developmental neurotoxicity of organophosphates such as chlorpyrifos (CPF) involves multiple mechanisms that ultimately compromise the function of specific neurotransmitter systems, notably acetylcholine (ACh) and serotonin (5-hydroxytryptamine, 5HT). Studies in mammalian models incorporate both direct effects on brain development and indirect effects mediated through maternal physiology and maternal/neonatal interactions. We examined the effects of CPF in an avian model, which does not share these potential confounds. Chick eggs were injected with CPF (10 or 20 mg/kg) on incubation days 2 and 6 and markers of ACh and 5HT systems were examined at hatching. The higher dose caused a reduction in cholinesterase activity but there was no consistent downregulation of m(2)-muscarinic ACh receptors as would have been expected from ACh hyperstimulation. Both doses evoked significant reductions in the presynaptic high-affinity choline transporter, the rate-limiting factor in ACh biosynthesis, as monitored by binding of hemicholinium-3. Choline acetyltransferase, a constitutive marker for ACh terminals, was unaffected. This suggests that CPF reduces ACh presynaptic activity rather than compromising the development of ACh projections per se. CPF exposure also reduced the expression of cerebrocortical 5HT(1A) receptors. These effects in the chick model recapitulate many of the actions of early gestational CPF exposure in rats, and thus suggest that CPF exerts direct actions on the immature brain to compromise the development of ACh and 5HT pathways.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
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Slotkin TA, Bodwell BE, Levin ED, Seidler FJ. Neonatal exposure to low doses of diazinon: long-term effects on neural cell development and acetylcholine systems. ENVIRONMENTAL HEALTH PERSPECTIVES 2008; 116:340-8. [PMID: 18335101 PMCID: PMC2265026 DOI: 10.1289/ehp.11005] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Accepted: 12/13/2007] [Indexed: 05/24/2023]
Abstract
BACKGROUND The developmental neurotoxicity of organophosphate pesticides involves mechanisms other than their shared property of cholinesterase inhibition. OBJECTIVES We gave diazinon (DZN) to newborn rats on postnatal days 1-4, using doses (0.5 or 2 mg/kg) spanning the threshold for barely detectable cholinesterase inhibition. METHODS We then evaluated the lasting effects on indices of neural cell number and size, and on functional markers of acetylcholine (ACh) synapses (choline acetyltransferase, presynaptic high-affinity choline transporter, nicotinic cholinergic receptors) in a variety of brain regions. RESULTS DZN exposure produced a significant overall increase in cell-packing density in adolescence and adulthood, suggestive of neuronal loss and reactive gliosis; however, some regions (temporal/occipital cortex, striatum) showed evidence of net cell loss, reflecting a greater sensitivity to neurotoxic effects of DZN. Deficits were seen in ACh markers in cerebrocortical areas and the hippocampus, regions enriched in ACh projections. In contrast, there were no significant effects in the midbrain, the major locus for ACh cell bodies. The striatum showed a unique pattern, with robust initial elevations in the ACh markers that regressed in adulthood to normal or subnormal values. CONCLUSIONS These results indicate that developmental exposures to apparently nontoxic doses of DZN compromise neural cell development and alter ACh synaptic function in adolescence and adulthood. The patterns seen here differ substantially from those seen in earlier work with chlorpyrifos, reinforcing the concept that the various organophosphates have fundamentally different effects on the developmental trajectories of specific neurotransmitter systems, unrelated to their shared action as cholinesterase inhibitors.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology & Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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Slotkin TA, Seidler FJ, Fumagalli F. Targeting of neurotrophic factors, their receptors, and signaling pathways in the developmental neurotoxicity of organophosphates in vivo and in vitro. Brain Res Bull 2008; 76:424-38. [PMID: 18502319 DOI: 10.1016/j.brainresbull.2008.01.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Revised: 12/11/2007] [Accepted: 01/01/2008] [Indexed: 11/16/2022]
Abstract
Neurotrophic factors control neural cell differentiation and assembly of neural circuits. We previously showed that organophosphate pesticides differentially regulate members of the fibroblast growth factor (fgf) gene family. We administered chlorpyrifos and diazinon to neonatal rats on postnatal days 1-4 at doses devoid of systemic toxicity or growth impairment, and spanning the threshold for barely-detectable cholinesterase inhibition. We evaluated the impact on gene families for different classes of neurotrophic factors. Using microarrays, we examined the regional expression of mRNAs encoding the neurotrophins (ntfs), brain-derived neurotrophic factor (bdnf), nerve growth factor (ngf), the wnt and fzd gene families and the corresponding receptors. Chlorpyrifos and diazinon both had widespread effects on the fgf, ntf, wnt and fzd families but much less on the bdnf and ngf groups. However, the two organophosphates showed disparate effects on a number of key neurotrophic factors. To determine if the actions were mediated directly on differentiating neurons, we tested chlorpyrifos in PC12 cells, an in vitro model of neural cell development. Effects in PC12 cells mirrored many of those for members of the fgf, ntf and wnt families, as well as the receptors for the ntfs, especially during early differentiation, the stage known to be most susceptible to disruption by organophosphates. Our results suggest that actions on neurotrophic factors provide a mechanism for the developmental neurotoxicity of low doses of organophosphates, and, since effects on expression of the affected genes differed with test agent, may help explain regional disparities in effects and critical periods of vulnerability.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology & Cancer Biology, Duke University Medical Center, Box 3813 DUMC, Durham, NC 27710, USA.
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Marty MS, Domoradzki JY, Hansen SC, Timchalk C, Bartels MJ, Mattsson JL. The Effect of Route, Vehicle, and Divided Doses on the Pharmacokinetics of Chlorpyrifos and Its Metabolite Trichloropyridinol in Neonatal Sprague-Dawley Rats. Toxicol Sci 2007; 100:360-73. [PMID: 17928393 DOI: 10.1093/toxsci/kfm239] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Mary Sue Marty
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, MI 48674, USA.
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Buznikov GA, Nikitina LA, Rakić LM, Milosević I, Bezuglov VV, Lauder JM, Slotkin TA. The sea urchin embryo, an invertebrate model for mammalian developmental neurotoxicity, reveals multiple neurotransmitter mechanisms for effects of chlorpyrifos: therapeutic interventions and a comparison with the monoamine depleter, reserpine. Brain Res Bull 2007; 74:221-31. [PMID: 17720543 PMCID: PMC2042487 DOI: 10.1016/j.brainresbull.2007.06.012] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Revised: 06/12/2007] [Accepted: 06/12/2007] [Indexed: 11/15/2022]
Abstract
Lower organisms show promise for the screening of neurotoxicants that might target mammalian brain development. Sea urchins use neurotransmitters as embryonic growth regulatory signals, so that adverse effects on neural substrates for mammalian brain development can be studied in this simple organism. We compared the effects of the organophosphate insecticide, chlorpyrifos in sea urchin embryos with those of the monoamine depleter, reserpine, so as to investigate multiple neurotransmitter mechanisms involved in developmental toxicity and to evaluate different therapeutic interventions corresponding to each neurotransmitter system. Whereas reserpine interfered with all stages of embryonic development, the effects of chlorpyrifos did not emerge until the mid-blastula stage. After that point, the effects of the two agents were similar. Treatment with membrane permeable analogs of the monoamine neurotransmitters, serotonin and dopamine, prevented the adverse effects of either chlorpyrifos or reserpine, despite the fact that chlorpyrifos works simultaneously through actions on acetylcholine, monoamines and other neurotransmitter pathways. This suggests that different neurotransmitters, converging on the same downstream signaling events, could work together or in parallel to offset the developmental disruption caused by exposure to disparate agents. We tested this hypothesis by evaluating membrane permeable analogs of acetylcholine and cannabinoids, both of which proved effective against chlorpyrifos- or reserpine-induced teratogenesis. Invertebrate test systems can provide both a screening procedure for mammalian neuroteratogenesis and may uncover novel mechanisms underlying developmental vulnerability as well as possible therapeutic approaches to prevent teratogenesis.
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Affiliation(s)
- Gennady A Buznikov
- N.K. Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
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Betancourt AM, Filipov NM, Carr RL. Alteration of neurotrophins in the hippocampus and cerebral cortex of young rats exposed to chlorpyrifos and methyl parathion. Toxicol Sci 2007; 100:445-55. [PMID: 17893397 DOI: 10.1093/toxsci/kfm248] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Exposure to either chlorpyrifos (CPS) or methyl parathion (MPS) results in the inhibition of acetylcholinesterase and leads to altered neuronal activity which normally regulates critical genes such as the neurotrophins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). The effects of postnatal exposure to CPS and MPS on the expression of messenger RNA (mRNA) and protein levels for NGF and BDNF were investigated in the frontal cerebral cortex (cortex) and hippocampus of rats. Oral administration of CPS (4.0 or 6.0 mg/kg), MPS (0.6 or 0.9 mg/kg), or the safflower oil vehicle was performed daily from postnatal day 10 (PND10) through PND20. Exposure induced significant effects on growth and cholinesterase activity. Increased NGF protein levels were observed in the hippocampus but not the cortex on PND20 with some reduction occurring on PND28 in both regions. These changes did not correlate with the changes in NGF mRNA. BDNF mRNA was increased in both regions on PND20 and PND28, whereas BDNF protein levels were increased on PND20. On PND12, c-fos mRNA, a marker of neuronal activation, was increased in both regions. Total BDNF protein was increased in the hippocampus but decreased in the cortex. No changes in NGF protein were observed. These results indicate that repeated developmental OP exposure during the postnatal period alters NGF and BDNF in the cortex and the hippocampus and the patterns of these alterations differ between regions.
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Affiliation(s)
- Angela M Betancourt
- Center for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA
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Slotkin TA, Seidler FJ, Fumagalli F. Exposure to organophosphates reduces the expression of neurotrophic factors in neonatal rat brain regions: similarities and differences in the effects of chlorpyrifos and diazinon on the fibroblast growth factor superfamily. ENVIRONMENTAL HEALTH PERSPECTIVES 2007; 115:909-16. [PMID: 17589599 PMCID: PMC1892141 DOI: 10.1289/ehp.9901] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Accepted: 02/27/2007] [Indexed: 05/16/2023]
Abstract
BACKGROUND The fibroblast growth factor (FGF) superfamily of neurotrophic factors plays critical roles in neural cell development, brain assembly, and recovery from neuronal injury. OBJECTIVES We administered two organophosphate pesticides, chlorpyrifos and diazinon, to neonatal rats on postnatal days 1-4, using doses below the threshold for systemic toxicity or growth impairment, and spanning the threshold for barely detectable cholinesterase inhibition: 1 mg/kg/day chlorpyrifos and 1 or 2 mg/kg/day diazinon. METHODS Using microarrays, we then examined the regional expression of mRNAs encoding the FGFs and their receptors (FGFRs) in the forebrain and brain stem. RESULTS Chlorpyrifos and diazinon both markedly suppressed fgf20 expression in the forebrain and fgf2 in the brain stem, while elevating brain stem fgfr4 and evoking a small deficit in brain stem fgf22. However, they differed in that the effects on fgf2 and fgfr4 were significantly larger for diazinon, and the two agents also showed dissimilar, smaller effects on fgf11, fgf14, and fgfr1. CONCLUSIONS The fact that there are similarities but also notable disparities in the responses to chlorpyrifos and diazinon, and that robust effects were seen even at doses that do not inhibit cholinesterase, supports the idea that organophosphates differ in their propensity to elicit developmental neurotoxicity, unrelated to their anticholinesterase activity. Effects on neurotrophic factors provide a mechanistic link between organophosphate injury to developing neurons and the eventual, adverse neurodevelopmental outcomes.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology & Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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Slotkin TA, Seidler FJ. Comparative developmental neurotoxicity of organophosphates in vivo: transcriptional responses of pathways for brain cell development, cell signaling, cytotoxicity and neurotransmitter systems. Brain Res Bull 2007; 72:232-74. [PMID: 17452286 PMCID: PMC1945108 DOI: 10.1016/j.brainresbull.2007.01.005] [Citation(s) in RCA: 171] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Revised: 12/15/2006] [Accepted: 01/09/2007] [Indexed: 11/17/2022]
Abstract
Organophosphates affect mammalian brain development through a variety of mechanisms beyond their shared property of cholinesterase inhibition. We used microarrays to characterize similarities and differences in transcriptional responses to chlorpyrifos and diazinon, assessing defined gene groupings for the pathways known to be associated with the mechanisms and/or outcomes of chlorpyrifos-induced developmental neurotoxicity. We exposed neonatal rats to daily doses of chlorpyrifos (1mg/kg) or diazinon (1 or 2mg/kg) on postnatal days 1-4 and evaluated gene expression profiles in brainstem and forebrain on day 5; these doses produce little or no cholinesterase inhibition. We evaluated pathways for general neural cell development, cell signaling, cytotoxicity and neurotransmitter systems, and identified significant differences for >60% of 252 genes. Chlorpyrifos elicited major transcriptional changes in genes involved in neural cell growth, development of glia and myelin, transcriptional factors involved in neural cell differentiation, cAMP-related cell signaling, apoptosis, oxidative stress, excitotoxicity, and development of neurotransmitter synthesis, storage and receptors for acetylcholine, serotonin, norepinephrine and dopamine. Diazinon had similar effects on many of the same processes but also showed major differences from chlorpyrifos. Our results buttress the idea that different organophosphates target multiple pathways involved in neural cell development but also that they deviate in key aspects that may contribute to disparate neurodevelopmental outcomes. Equally important, these pathways are compromised at exposures that are unrelated to biologically significant cholinesterase inhibition and its associated signs of systemic toxicity. The approach used here demonstrates how planned comparisons with microarrays can be used to screen for developmental neurotoxicity.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology & Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
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Slotkin TA, Seidler FJ. Developmental exposure to terbutaline and chlorpyrifos, separately or sequentially, elicits presynaptic serotonergic hyperactivity in juvenile and adolescent rats. Brain Res Bull 2007; 73:301-9. [PMID: 17562396 PMCID: PMC1986775 DOI: 10.1016/j.brainresbull.2007.04.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2007] [Revised: 04/17/2007] [Accepted: 04/17/2007] [Indexed: 11/29/2022]
Abstract
Developmental exposure to unrelated neurotoxicants can nevertheless converge on common final targets so as to exacerbate damage or functional deficits. We examined the effects of developmental exposure to terbutaline, a beta2-adrenergic receptor agonist used to arrest preterm labor, and chlorpyrifos, a widely used organophosphate pesticide, on serotonin (5HT) systems. Treatments were chosen to parallel periods typical of human developmental exposures, terbutaline (10 mg/kg) on postnatal days (PN) 2-5 and chlorpyrifos (5 mg/kg) on PN11-14, with assessments conducted in juvenile and adolescent stages (PN21, PN30 and PN45), comparing each agent alone as well as sequential administration of both. By itself, terbutaline produced persistent 5HT presynaptic hyperactivity as evidenced by increased 5HT turnover in brain regions containing 5HT terminal zones; this effect was similar to that seen in earlier studies with chlorpyrifos administration during the same early postnatal period. Later administration of chlorpyrifos (PN11-14) produced a transient increase in 5HT turnover during the juvenile stage, and the sequential exposure paradigm, terbutaline followed by chlorpyrifos, showed a corresponding increase in effect over either agent alone. In combination with our earlier work on 5HT receptors, these results indicate that terbutaline is a developmental neurotoxicant that targets the 5HT system, findings that lend a mechanistic underpinning to clinical indications of elevated childhood psychiatric disorders in the offspring of women treated with beta-agonist tocolytics. Equally importantly, the interaction between terbutaline and chlorpyrifos suggests that tocolytic therapy may alter the subsequent susceptibility to common environmental toxicants.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
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71
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Slotkin TA, MacKillop EA, Ryde IT, Tate CA, Seidler FJ. Screening for developmental neurotoxicity using PC12 cells: comparisons of organophosphates with a carbamate, an organochlorine, and divalent nickel. ENVIRONMENTAL HEALTH PERSPECTIVES 2007; 115:93-101. [PMID: 17366826 PMCID: PMC1797840 DOI: 10.1289/ehp.9527] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/19/2006] [Accepted: 09/06/2006] [Indexed: 05/14/2023]
Abstract
BACKGROUND In light of the large number of chemicals that are potential developmental neurotoxicants, there is a need to develop rapid screening techniques. OBJECTIVES We exposed undifferentiated and differentiating neuronotypic PC12 cells to different organophosphates (chlorpyrifos, diazinon, parathion), a carbamate (physostigmine), an organochlorine (dieldrin), and a metal (divalent nickel; Ni2+) and examined indices of cell replication and differentiation for both short- and long-term exposures. RESULTS In undifferentiated cells, all the agents inhibited DNA synthesis, with the greatest effect for diazinon, but physostigmine eventually produced the largest deficits in the total number of cells after prolonged exposure. The onset of differentiation intensified the adverse effects on DNA synthesis and changed the rank order in keeping with a shift away from noncholinergic mechanisms and toward cholinergic mechanisms. Differentiation also worsened the effects of each agent on cell number after prolonged exposure, whereas cell growth was not suppressed, nor were there any effects on viability as assessed with trypan blue. Nevertheless, differentiating cells displayed signs of oxidative stress from all of the test compounds except Ni2+, as evidenced by measurements of lipid peroxidation. Finally, all of the toxicants shifted the transmitter fate of the cells away from the cholinergic phenotype and toward the catecholaminergic phenotype. CONCLUSIONS These studies point out the feasibility of developing cell-based screening methods that enable the detection of multiple end points that may relate to mechanisms associated with developmental neurotoxicity, revealing some common targets for disparate agents.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology & Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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Rauh VA, Garfinkel R, Perera FP, Andrews HF, Hoepner L, Barr DB, Whitehead R, Tang D, Whyatt RW. Impact of prenatal chlorpyrifos exposure on neurodevelopment in the first 3 years of life among inner-city children. Pediatrics 2006; 118:e1845-59. [PMID: 17116700 PMCID: PMC3390915 DOI: 10.1542/peds.2006-0338] [Citation(s) in RCA: 481] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE The purpose of this study was to investigate the impact of prenatal exposure to chlorpyrifos on 3-year neurodevelopment and behavior in a sample of inner-city minority children. METHODS As part of an ongoing prospective cohort study in an inner-city minority population, neurotoxicant effects of prenatal exposure to chlorpyrifos were evaluated in 254 children through the first 3 years of life. This report examined cognitive and motor development at 12, 24, and 36 months (measured with the Bayley Scales of Infant Development II) and child behavior at 36 months (measured with the Child Behavior Checklist) as a function of chlorpyrifos levels in umbilical cord plasma. RESULTS Highly exposed children (chlorpyrifos levels of >6.17 pg/g plasma) scored, on average, 6.5 points lower on the Bayley Psychomotor Development Index and 3.3 points lower on the Bayley Mental Development Index at 3 years of age compared with those with lower levels of exposure. Children exposed to higher, compared with lower, chlorpyrifos levels were also significantly more likely to experience Psychomotor Development Index and Mental Development Index delays, attention problems, attention-deficit/hyperactivity disorder problems, and pervasive developmental disorder problems at 3 years of age. CONCLUSIONS The adjusted mean 36-month Psychomotor Development Index and Mental Development Index scores of the highly and lower exposed groups differed by only 7.1 and 3.0 points, respectively, but the proportion of delayed children in the high-exposure group, compared with the low-exposure group, was 5 times greater for the Psychomotor Development Index and 2.4 times greater for the Mental Development Index, increasing the number of children possibly needing early intervention services.
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Affiliation(s)
- Virginia A Rauh
- Columbia Center for Children's Environmental Health, Mailman School of Public Health, Columbia University, 60 Haven Ave, B-109, New York, NY 10032, USA.
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Kaufmann W, Gröters S. Developmental neuropathology in DNT-studies—A sensitive tool for the detection and characterization of developmental neurotoxicants. Reprod Toxicol 2006; 22:196-213. [PMID: 16781841 DOI: 10.1016/j.reprotox.2006.04.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Revised: 04/10/2006] [Accepted: 04/10/2006] [Indexed: 11/18/2022]
Abstract
Developmental neurotoxicity (DNT-) studies are the first reproduction toxicity studies for which an extended histopathological examination of developing structures is required by the current EPA and OECD guidelines. The morphological screening includes a macroscopic evaluation of the brain and nervous tissue, brain weight parameters, gross morphometry of the brain, neurohistological examinations and a quantitative analysis of major brain areas. This review is intended to give an overview about the needs according to guideline requirements, practical approaches for a successful developmental neuropathology and its preconditions and does include examples of background data on the value and functional meaning of morphological data. A selection of experimental data from literature is also presented in the light of their contribution for the understanding of important, neurodevelopmental disorders in humans.
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Affiliation(s)
- Wolfgang Kaufmann
- Department of Product Safety, Regulations, Experimental Toxicology and Ecology, BASF AG, Ludwigshafen, Germany.
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Ricceri L, Venerosi A, Capone F, Cometa MF, Lorenzini P, Fortuna S, Calamandrei G. Developmental neurotoxicity of organophosphorous pesticides: fetal and neonatal exposure to chlorpyrifos alters sex-specific behaviors at adulthood in mice. Toxicol Sci 2006; 93:105-13. [PMID: 16760416 DOI: 10.1093/toxsci/kfl032] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Developmental exposure to the organophosphorous insecticide chlorpyrifos (CPF) induces long-term effects on brain and behavior in laboratory rodents. We evaluated in adult mice the behavioral effects of either fetal and/or neonatal CPF exposure at doses not inhibiting fetal and neonatal brain cholinesterase. CPF (3 or 6 mg/kg) was given by oral treatment to pregnant females on gestational days 15-18 and offspring were treated sc (1 or 3 mg/kg) on postnatal days (PNDs) 11-14. Serum and brain acetylcholinesterase (AChE) activity was evaluated at birth and 24 h from termination of postnatal treatments. On PND 70, male mice were assessed for spontaneous motor activity in an open-field test and in a socioagonistic encounter with an unfamiliar conspecific. Virgin females underwent a maternal induction test following presentation of foster pups. Both sexes were subjected to a plus-maze test to evaluate exploration and anxiety levels. Gestational and postnatal CPF exposure (higher doses) affected motor activity in the open field and enhanced synergically agonistic behavior. Postnatal CPF exposure increased maternal responsiveness toward pups in females. Mice of both sexes exposed to postnatal CPF showed reduced anxiety response in the plus-maze, an effect greater in females. Altogether, developmental exposure to CPF at doses that do not cause brain AChE inhibition induces long-term alterations in sex-specific behavior patterns of the mouse species. Late neonatal exposure on PNDs 11-14 was the most effective in causing behavioral changes. These findings support the hypothesis that developmental CPF may represent a risk factor for increased vulnerability to neurodevelopmental disorders in humans.
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Affiliation(s)
- Laura Ricceri
- Section of Behavioral Neurosciences, Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Viale Regina Elena 299, I-00161 Roma, Italy
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Venerosi A, Calamandrei G, Ricceri L. A social recognition test for female mice reveals behavioral effects of developmental chlorpyrifos exposure. Neurotoxicol Teratol 2006; 28:466-71. [PMID: 16814983 DOI: 10.1016/j.ntt.2006.05.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2006] [Revised: 04/27/2006] [Accepted: 05/13/2006] [Indexed: 11/20/2022]
Abstract
CD-1 mice were exposed to the organophosphate pesticide chlorpyrifos (CPF) both prenatally (gestational days 15-18; doses 0, 3 or 6 mg/kg) and postnatally (postnatal days 11-14, doses 0, 1 or 3 mg/kg). When four-month-olds, females underwent a social recognition test in which ultrasound vocalizations (USVs) and social investigation behavior emitted by a resident female in the presence of a female partner were measured during two subsequent 3 min sessions (interval between the two sessions 45 min). Throughout the social recognition test a marked increase in USVs was found in females prenatally treated with the highest CPF dose; USV increase was also paralleled by a selective increase in frequency and not in duration of social investigation. These results confirm that developmental exposure to CPF induces long-lasting alterations in the social behavior repertoire of the mouse, thus extending our previous observations on the effects of postnatal CPF on male agonistic behavior to the female sex. They also suggest that social recognition can be easily and rapidly assessed in the female mouse making it possible to evaluate, primarily by means of USV emission, even subtle alteration of social behavioral patterns dissociated from cognitive components of individual recognition.
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Affiliation(s)
- Aldina Venerosi
- Section of Behavioural Neuroscience, Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, V.le Regina Elena 299 I-00161 Rome, Italy
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Jameson RR, Seidler FJ, Qiao D, Slotkin TA. Chlorpyrifos affects phenotypic outcomes in a model of mammalian neurodevelopment: critical stages targeting differentiation in PC12 cells. ENVIRONMENTAL HEALTH PERSPECTIVES 2006; 114:667-72. [PMID: 16675418 PMCID: PMC1459917 DOI: 10.1289/ehp.8750] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The organophosphate insecticide chlorpyrifos (CPF) adversely affects mammalian brain development through multiple mechanisms. To determine if CPF directly affects neuronal cell replication and phenotypic fate, and to identify the vulnerable stages of differentiation, we exposed PC12 cells, a model for mammalian neurodevelopment, to CPF concentrations spanning the threshold for cholinesterase inhibition (5-50 microM) and conducted evaluations during mitosis and in early and mid-differentiation. In undifferentiated cells, exposure to 5 microM CPF for 1-3 days reduced DNA synthesis significantly without eliciting cytotoxicity. At the same time, CPF increased the expression of tyrosine hydroxylase (TH), the enzymatic marker for the catecholamine phenotype, without affecting choline acetyltransferase (ChAT), the corresponding marker for the cholinergic phenotype. Upon exposure to nerve growth factor (NGF), PC12 cells developed neuritic projections in association with vastly increased TH and ChAT expression accompanying differentiation into the two phenotypes. CPF exposure begun at the start of differentiation significantly reduced ChAT but not TH activity. In contrast, when CPF was added in mid-differentiation (4 days of NGF pretreatment), ChAT was unaffected and TH was increased slightly. Thus, CPF exerts stage-specific effects, reducing DNA synthesis in the undifferentiated state, impairing development of the cholinergic phenotype at the start of differentiation, and promoting expression of the catecholaminergic phenotype both in undifferentiated and differentiated cells. CPF administration in vivo produces deficits in the number of neurons and cholinergic function, and because we were able to reproduce these effects in vitro, our results suggest that CPF directly influences the phenotypic fate of neuronal precursors.
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Affiliation(s)
- Ruth R Jameson
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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Slotkin TA, Levin ED, Seidler FJ. Comparative developmental neurotoxicity of organophosphate insecticides: effects on brain development are separable from systemic toxicity. ENVIRONMENTAL HEALTH PERSPECTIVES 2006; 114:746-51. [PMID: 16675431 PMCID: PMC1459930 DOI: 10.1289/ehp.8828] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
A comparative approach to the differences between systemic toxicity and developmental neurotoxicity of organophosphates is critical to determine the degree to which multiple mechanisms of toxicity carry across different members of this class of insecticides. We contrasted neuritic outgrowth and cholinergic synaptic development in neonatal rats given different organophosphates (chlorpyrifos, diazinon, parathion) at doses spanning the threshold for impaired growth and viability. Animals were treated daily on postnatal days 1-4 by subcutaneous injection so as to bypass differences in first-pass activation to the oxon or catabolism to inactive products. Evaluations occurred on day 5. Parathion (maximum tolerated dose, 0.1 mg/kg) was far more systemically toxic than was chlorpyrifos or diazinon (maximum tolerated dose, 1-5 mg/kg). Below the maximum tolerated dose, diazinon impaired neuritic outgrowth in the forebrain and brainstem, evidenced by a deficit in the ratio of membrane protein to total protein. Diazinon also decreased choline acetyltransferase activity, a cholinergic neuronal marker, whereas it did not affect hemicholinium-3 binding to the presynaptic choline transporter, an index of cholinergic neuronal activity. There was no m(subscript)2(/subscript)-muscarinic acetylcholine receptor down-regulation, as would have occurred with chronic cholinergic hyperstimulation. The same pattern was found previously for chlorpyrifos. In contrast, parathion did not elicit any of these changes at its maximum tolerated dose. These results indicate a complete dichotomy between the systemic toxicity of organophosphates and their propensity to elicit developmental neurotoxicity. For parathion, the threshold for lethality lies below that necessary for adverse effects on brain development, whereas the opposite is true for chlorpyrifos and diazinon.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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Gultekin F, Patat S, Akca H, Akdogan M, Altuntas I. Melatonin can suppress the cytotoxic effects of chlorpyrifos on human hepG2 cell lines. Hum Exp Toxicol 2006; 25:47-55. [PMID: 16539209 DOI: 10.1191/0960327106ht584oa] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The cytotoxic effect of chlorpyrifos (CP) on human HepG2 cell lines and the protective role of melatonin were investigated. TD50 of CP for HepGZ cells was also determined. The viability of HepGZ cells decreased with CP treatment in a dose-dependent manner (P <0.05). Preincubation with melatonin prior to CP application caused an increase in cell viability (P <0.05). TD50 of CP for HepG2 was determined as 84.5 microg/mL. A 1-hour melatonin treatment caused a decrease in TD50 from 84.5 to 34.1 microg/mL. The level of thiobarbituric acid reactive substance (TBARS) and the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) were determined in cell lines with or without melatonin administration to find out the possible mechanism of melatonin. CP caused a significant decrease in SOD, GSH-Px and CAT activities and an increase in TBARS level (P <0.05). Pre-incubation of cells with melatonin prevented an increase in TBARS. Melatonin also reduced the CP-caused inhibition of the activities of GSH-Px and CAT (P <0.05). It was suggested that CP shows a cytotoxic effect on HepG2 cell lines and melatonin can suppress cytotoxicity caused by CP with its antioxidant properties. Melatonin also reduces TD50 of CP for HepG2 cell lines.
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Affiliation(s)
- F Gultekin
- Department of Biochemistry, School of Medicine, Suleyman Demirel University, Isparta, Turkey.
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Slotkin TA, Tate CA, Cousins MM, Seidler FJ. Imbalances emerge in cardiac autonomic cell signaling after neonatal exposure to terbutaline or chlorpyrifos, alone or in combination. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2005; 160:219-30. [PMID: 16256208 DOI: 10.1016/j.devbrainres.2005.09.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Revised: 09/13/2005] [Accepted: 09/16/2005] [Indexed: 11/19/2022]
Abstract
During early neonatal development, the future reactivity of the heart to cardiac autonomic stimulation is programmed by the timing and intensity of the arrival of parasympathetic and sympathetic inputs. In neonatal rats, we examined the effects of exposure to terbutaline, a beta-adrenoceptor (betaAR) agonist used to arrest preterm labor, and chlorpyrifos (CPF), a widely used organophosphate pesticide that acts in part through inhibition of cholinesterase, using scenarios mimicking the likely developmental stages corresponding to peak human exposures: postnatal days (PN) 2-5 for terbutaline and PN11-14 for CPF. Terbutaline evoked a progressive deficit in cardiac betaAR binding but did not interfere with the ability of the receptors to stimulate adenylyl cyclase (AC). Terbutaline also reduced expression of m2 muscarinic acetylcholine receptors and suppressed their ability to inhibit AC. Surprisingly, CPF produced similar actions, a decrement in betaAR and m2 muscarinic receptor binding and a loss of the cholinergic AC response, and also augmented the ability of betaARs to stimulate AC. The effects of CPF are thus unlikely to reside in cholinergic hyperstimulation resulting from cholinesterase inhibition but instead involve other actions converging on receptors and cell signaling. Exposure to both agents, terbutaline followed by CPF, produced a summation of the two individual effects. Our findings at the level of cell signaling thus indicate that neonatal exposure to terbutaline or CPF, or sequentially to both agents, results in an imbalance of cardiac autonomic inputs favoring increased excitability, an outcome that may have an impact on cardiovascular responses.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Box 3813 DUMC, Durham, NC 27710, USA.
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Connors SL, Crowell DE, Eberhart CG, Copeland J, Newschaffer CJ, Spence SJ, Zimmerman AW. beta2-adrenergic receptor activation and genetic polymorphisms in autism: data from dizygotic twins. J Child Neurol 2005; 20:876-84. [PMID: 16417856 DOI: 10.1177/08830738050200110401] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Gestational and genetic factors can contribute to autism during infancy and early childhood through their effects on fetal brain development. Previous twin studies have shown strong genetic components for the development of autism, a disorder that can have multiple causes. We investigated the effects of prenatal overstimulation of the beta2-adrenergic receptor in dizygotic twins who were exposed to terbutaline, a selective beta2-adrenergic receptor agonist used to treat premature labor, as a gestational factor. As a possible genetic mechanism, we studied two beta2-adrenergic receptor polymorphisms in twins from whom DNA was available: glycine substitution at codon 16 (16G) and glutamic acid substitution at codon 27 (27E), which show diminished desensitization in vivo compared with the wild-type receptor. Continuous terbutaline exposure for 2 weeks or longer was associated with increased concordance for autism spectrum disorders in dizygotic twins (relative risk = 2.0), with a further increase in the risk for male twins with no other affected siblings (relative risk = 4.4). A significant association was found between the presence of 16G and 27E polymorphisms in autistic patients compared with population controls (P = .006). Prenatal overstimulation of the beta2-adrenergic receptor by terbutaline or by increased signaling of genetic polymorphisms of the beta2-adrenergic receptor that have diminished desensitization can affect cellular responses and developmental programs in the fetal brain, leading to autism.
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Affiliation(s)
- Susan L Connors
- Department of Neurology and Developmental Medicine, Kennedy Krieger Institute, Baltimore, MD 21205, USA
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81
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Brimijoin S. Can cholinesterase inhibitors affect neural development? ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2005; 19:429-432. [PMID: 21783508 DOI: 10.1016/j.etap.2004.12.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Accumulating evidence supports the view that acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) can influence the proliferation and differentiation of nerve cells. AChE in particular has been found to promote neurite outgrowth in a variety of model systems, possibly by serving as an adhesion molecule. Thus one might suspect that cholinesterase inhibitors would disturb neuronal development, with long-term implications for structure and function in the central and peripheral nervous systems. The actual picture is more complex because AChE's effects on neurite outgrowth may reflect protein-protein interactions that are not directly related to catalytic function but are nonetheless influenced by ligands with special structural features. The putative structural interactions have not yet been rigorously defined, but they are likely to involve enzyme regions at or near the peripheral anionic site. In addition to such effects, some organophosphorus anticholinesterases have been reported to act by still other mechanisms to depress macromolecule synthesis and cell survival in the developing brain. Taken together, this emerging information highlights the potential importance of anticholinesterase agents in developmental neurotoxicology.
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Affiliation(s)
- Stephen Brimijoin
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, 200 First Street, S.W., Rochester, MN 55905, USA
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82
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Aldridge JE, Levin ED, Seidler FJ, Slotkin TA. Developmental exposure of rats to chlorpyrifos leads to behavioral alterations in adulthood, involving serotonergic mechanisms and resembling animal models of depression. ENVIRONMENTAL HEALTH PERSPECTIVES 2005; 113:527-31. [PMID: 15866758 PMCID: PMC1257542 DOI: 10.1289/ehp.7867] [Citation(s) in RCA: 181] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
Developmental exposure to chlorpyrifos (CPF) causes persistent changes in serotonergic (5HT) systems. We administered 1 mg/kg/day CPF to rats on postnatal days 1-4, a regimen below the threshold for systemic toxicity. When tested in adulthood, CPF-exposed animals showed abnormalities in behavioral tests that involve 5HT mechanisms. In the elevated plus maze, males treated with CPF spent more time in the open arms, an effect seen with 5HT deficiencies in animal models of depression. Similarly, in an anhedonia test, the CPF-exposed group showed a decreased preference for chocolate milk versus water. Developmental CPF exposure also has lasting effects on cognitive function. We replicated our earlier finding that developmental CPF exposure ablates the normal sex differences in 16-arm radial maze learning and memory: during acquisition training, control male rats typically perform more accurately than do control females, but CPF treatment eliminated this normal sex difference. Females exposed to CPF showed a reduction in working and reference memory errors down to the rate of control males. Conversely, CPF-exposed males exhibited an increase in working and reference memory errors. After radial-arm acquisition training, we assessed the role of 5HT by challenging the animals with the 5HT2 receptor antagonist ketanserin. Ketanserin did not affect performance in controls but elicited dose-dependent increases in working and reference memory errors in the CPF group, indicating an abnormal dependence on 5HT systems. Our results indicate that neonatal CPF exposures, classically thought to be subtoxic, produce lasting changes in 5HT-related behaviors that resemble animal models of depression.
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Affiliation(s)
- Justin E Aldridge
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27701, USA
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83
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Garcia SJ, Seidler FJ, Slotkin TA. Developmental neurotoxicity of chlorpyrifos: targeting glial cells. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2005; 19:455-461. [PMID: 21783512 DOI: 10.1016/j.etap.2004.12.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The pesticide chlorpyrifos (CPF) causes neurobehavioral damage, even at doses that do not elicit acute cholinergic toxicity. CPF disrupts the developing brain during glial proliferation and differentiation. Since glial cells play critical roles in brain development and function, we hypothesized that CPF neurotoxicity involves alteration of glial cell development. CPF effects in C6 glioma cells mirrored effects in the intact brain: inhibited DNA synthesis; interfered with adenylyl cyclase (AC) signaling; obstructed DNA binding to transcription factors involved in cell differentiation; and enhanced reactive oxygen species (ROS) formation. CPF was administered to prenatal and neonatal rats and examined for markers of astrocytes, oligodendrocytes, and neurons. Widespread effects were elicited by exposure during the peak period of gliogenesis. Males were preferentially targeted during postnatal exposures while females experienced delayed effects following gestational exposure, commensurate with behavioral outcomes. Alterations in glial cell development contribute to CPF neurotoxicity, extending vulnerability to myelination, synaptic plasticity, and architectural modeling, which continue into adolescence.
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Affiliation(s)
- Stephanie J Garcia
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, NC 27710, USA
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84
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Aldridge JE, Meyer A, Seidler FJ, Slotkin TA. Developmental exposure to terbutaline and chlorpyrifos: pharmacotherapy of preterm labor and an environmental neurotoxicant converge on serotonergic systems in neonatal rat brain regions. Toxicol Appl Pharmacol 2005; 203:132-44. [PMID: 15710174 DOI: 10.1016/j.taap.2004.08.002] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Accepted: 08/04/2004] [Indexed: 11/29/2022]
Abstract
Developmental exposure to unrelated neurotoxicants can nevertheless produce similar neurobehavioral outcomes. We examined the effects of developmental exposure to terbutaline, a tocolytic beta2-adrenoceptor agonist used to arrest preterm labor, and chlorpyrifos (CPF), a widely used organophosphate pesticide, on serotonin (5HT) systems. Treatments were chosen to parallel periods typical of human developmental exposures, terbutaline (10 mg/kg) on postnatal days (PN) 2-5 and CPF (5 mg/kg) on PN11-14, with assessments conducted on PN45, comparing each agent alone as well as sequential administration of both. Although neither treatment affected growth or viability, each elicited similar alterations in factors that are critical to the function of the 5HT synapse: 5HT1A receptors, 5HT2 receptors, and the presynaptic 5HT transporter (5HTT). Either agent elicited global increases in 5HT receptors and the 5HTT in brain regions possessing 5HT cell bodies (midbrain, brainstem) as well as in the hippocampus, which contains 5HT projections. For both terbutaline and CPF, males were affected more than females, although there were some regional disparities in the sex selectivity between the two agents. Both altered 5HT receptor-mediated cell signaling, suppressing stimulatory effects on adenylyl cyclase and enhancing inhibitory effects. When animals were exposed sequentially to both agents, the outcomes were no more than additive and, for many effects, less than additive, suggesting convergence of the two agents on a common set of developmental mechanisms. Our results indicate that 5HT systems represent a target for otherwise unrelated neuroteratogens.
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MESH Headings
- Adenylyl Cyclase Inhibitors
- Adenylyl Cyclases/metabolism
- Animals
- Animals, Newborn
- Brain/drug effects
- Brain/metabolism
- Chlorpyrifos/administration & dosage
- Chlorpyrifos/toxicity
- Female
- Insecticides/administration & dosage
- Insecticides/toxicity
- Male
- Membrane Glycoproteins/metabolism
- Membrane Transport Proteins/metabolism
- Nerve Tissue Proteins/metabolism
- Pregnancy
- Prenatal Exposure Delayed Effects
- Rats
- Rats, Sprague-Dawley
- Receptors, Serotonin, 5-HT1/drug effects
- Receptors, Serotonin, 5-HT1/metabolism
- Receptors, Serotonin, 5-HT2/drug effects
- Receptors, Serotonin, 5-HT2/metabolism
- Serotonin
- Serotonin Plasma Membrane Transport Proteins
- Sex Factors
- Teratogens/toxicity
- Terbutaline/administration & dosage
- Terbutaline/toxicity
- Tocolytic Agents/administration & dosage
- Tocolytic Agents/toxicity
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Affiliation(s)
- Justin E Aldridge
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
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85
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Meyer A, Seidler FJ, Aldridge JE, Slotkin TA. Developmental exposure to terbutaline alters cell signaling in mature rat brain regions and augments the effects of subsequent neonatal exposure to the organophosphorus insecticide chlorpyrifos. Toxicol Appl Pharmacol 2005; 203:154-66. [PMID: 15710176 DOI: 10.1016/j.taap.2004.08.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2004] [Accepted: 08/12/2004] [Indexed: 11/25/2022]
Abstract
Exposure to apparently unrelated neurotoxicants can nevertheless converge on common neurodevelopmental events. We examined the long-term effects of developmental exposure of rats to terbutaline, a beta-adrenoceptor agonist used to arrest preterm labor, and the organophosphorus insecticide chlorpyrifos (CPF) separately and together. Treatments mimicked the appropriate neurodevelopmental stages for human exposures: terbutaline on postnatal days (PN) 2-5 and CPF on PN11-14, with assessments conducted on PN45. Although neither treatment affected growth or viability, each elicited alterations in CNS cell signaling mediated by adenylyl cyclase (AC), a transduction pathway shared by numerous neuronal and hormonal signals. Terbutaline altered signaling in the brainstem and cerebellum, with gender differences particularly notable in the cerebellum (enhanced AC in males, suppressed in females). By itself, CPF exposure elicited deficits in AC signaling in the midbrain, brainstem, and striatum. However, sequential exposure to terbutaline followed by CPF produced larger alterations and involved a wider spectrum of brain regions than were obtained with either agent alone. In the cerebral cortex, adverse effects of the combined treatment intensified between PN45 and PN60, suggesting that exposures alter the long-term program for development of synaptic communication, leading to alterations in AC signaling that emerge even after adolescence. These findings indicate that terbutaline, like CPF, is a developmental neurotoxicant, and reinforce the idea that its use in preterm labor may create a subpopulation that is sensitized to long-term CNS effects of organophosphorus insecticides.
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Affiliation(s)
- Armando Meyer
- Centro de Estudos da Saúde do Trabalhador e Ecologia Humana (AM), Escola Nacional de Saúde Pública, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil
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86
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Zurich MG, Honegger P, Schilter B, Costa LG, Monnet-Tschudi F. Involvement of glial cells in the neurotoxicity of parathion and chlorpyrifos. Toxicol Appl Pharmacol 2004; 201:97-104. [PMID: 15541749 DOI: 10.1016/j.taap.2004.05.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2004] [Accepted: 05/03/2004] [Indexed: 11/15/2022]
Abstract
An in vitro model, the aggregating brain cell culture of fetal rat telencephalon, has been used to investigate the influence of glial cells on the neurotoxicity of two organophosphorus pesticides (OPs), chlorpyrifos and parathion. Mixed-cell aggregate cultures were treated continuously for 10 days between DIV 5 and 15. Parathion induced astrogliosis at concentration at which MAP-2 immunostaining, found here to be more sensitive than neuron-specific enzyme activities, was not affected. In contrast, chlorpyrifos induced a comparatively weak gliotic reaction, and only at concentrations at which neurons were already affected. After similar treatments, increased neurotoxicity of parathion and chlorpyrifos was found in aggregate cultures deprived of glial cells. These results suggest that glial cells provide neuroprotection against OPs toxicity. To address the question of the difference in toxicity between parathion and chlorpyrifos, the toxic effects of their leaving groups, p-nitrophenol and trichloropyridinol, were studied in mixed-cell aggregates. General cytotoxicity was more pronounced for trichloropyridinol and both compounds had similar toxic effects on neuron-specific enzyme activities. In contrast, trichloropyridinol induced a much stronger decrease in glutamine synthetase activity, the enzymatic marker of astrocytes. Trichloropyridinol may exert a toxic effect on astrocytes, compromising their neuroprotective function, thus exacerbating the neurotoxicity of chlorpyrifos. This is in line with the suggestion that glial cells may contribute to OPs neurotoxicity, and with the view that OPs may exert their neurotoxic effects through different mechanisms.
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Affiliation(s)
- M-G Zurich
- Department of Physiology, University of Lausanne, Lausanne, Switzerland.
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87
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Slotkin TA. Cholinergic systems in brain development and disruption by neurotoxicants: nicotine, environmental tobacco smoke, organophosphates. Toxicol Appl Pharmacol 2004; 198:132-51. [PMID: 15236950 DOI: 10.1016/j.taap.2003.06.001] [Citation(s) in RCA: 402] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2003] [Accepted: 06/09/2003] [Indexed: 12/22/2022]
Abstract
Acetylcholine and other neurotransmitters play unique trophic roles in brain development. Accordingly, drugs and environmental toxicants that promote or interfere with neurotransmitter function evoke neurodevelopmental abnormalities by disrupting the timing or intensity of neurotrophic actions. The current review discusses three exposure scenarios involving acetylcholine systems: nicotine from maternal smoking during pregnancy, exposure to environmental tobacco smoke (ETS), and exposure to the organophosphate insecticide, chlorpyrifos (CPF). All three have long-term, adverse effects on specific processes involved in brain cell replication and differentiation, synaptic development and function, and ultimately behavioral performance. Many of these effects can be traced to the sequence of cellular events surrounding the trophic role of acetylcholine acting on its specific cellular receptors and associated signaling cascades. However, for chlorpyrifos, additional noncholinergic mechanisms appear to be critical in establishing the period of developmental vulnerability, the sites and type of neural damage, and the eventual outcome. New findings indicate that developmental neurotoxicity extends to late phases of brain maturation including adolescence. Novel in vitro and in vivo exposure models are being developed to uncover heretofore unsuspected mechanisms and targets for developmental neurotoxicants.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
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88
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Rhodes MC, Seidler FJ, Qiao D, Tate CA, Cousins MM, Slotkin TA. Does pharmacotherapy for preterm labor sensitize the developing brain to environmental neurotoxicants? Cellular and synaptic effects of sequential exposure to terbutaline and chlorpyrifos in neonatal rats. Toxicol Appl Pharmacol 2004; 195:203-17. [PMID: 14998686 DOI: 10.1016/j.taap.2003.11.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2003] [Accepted: 11/10/2003] [Indexed: 11/29/2022]
Abstract
It is increasingly clear that environmental toxicants target specific human subpopulations. In the current study, we examined the effects of prior developmental exposure to a beta(2)-adrenoceptor agonist used to arrest preterm labor, terbutaline, on the subsequent effects of exposure to the organophosphate insecticide, chlorpyrifos (CPF). Neonatal rats were given terbutaline on postnatal day (PN) 2-5, followed by CPF on PN11-14. Although neither treatment affected growth or viability, each elicited alterations in indices of brain cell differentiation and cholinergic innervation in the immediate posttreatment period (PN15), persisting into adulthood (PN60). Biomarkers of brain cell number (DNA concentration and content), cell size (protein/DNA ratio) and neuritic projections (membrane/total protein) were affected by either agent alone, with patterns consistent with neuronal and neuritic damage accompanied by reactive gliosis. The combined exposure augmented these effects by both additive and synergistic mechanisms. Similarly, choline acetyltransferase (ChAT), a constitutive marker for cholinergic nerve terminals, was affected only by combined exposure to both terbutaline and CPF. Indices of cholinergic synaptic activity [hemicholinium-3 and m(2)-muscarinic acetylcholine receptor binding] showed impairment after exposure to either terbutaline or CPF but the effects were more severe when the treatments were combined. These findings suggest that terbutaline, like CPF, is a developmental neurotoxicant, and that its use in the therapy of preterm labor may create a subpopulation that is sensitized to the adverse neural effects of a subsequent exposure to organophosphate insecticides.
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Affiliation(s)
- Melissa C Rhodes
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
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89
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Roy TS, Seidler FJ, Slotkin TA. Morphologic effects of subtoxic neonatal chlorpyrifos exposure in developing rat brain: regionally selective alterations in neurons and glia. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2004; 148:197-206. [PMID: 14766197 DOI: 10.1016/j.devbrainres.2003.12.004] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/18/2003] [Indexed: 10/26/2022]
Abstract
The widely used organophosphate insecticide, chlorpyrifos (CPF), elicits neurobehavioral teratogenesis with exposure windows ranging from the embryonic neural tube stage through postnatal development. To explore the morphologic changes occurring in late-stage exposure, newborn rats were given 5 mg/kg of CPF s.c. daily on postnatal days (PN) 11-14, a regimen that is devoid of systemic toxicity, but that elicits long-term cognitive impairment. On PN15 and 20, we examined the septal nucleus, striatum and somatosensory cortex. Across all three regions, CPF elicited a significant decrease in the number of glial cells. Superimposed on this basic pattern, there were region-specific alterations in the number and type of neurons, and neuronal perikaryal dimensions. In the septal nucleus, the CPF group exhibited an increase in the number of neurons on PN20, representing a delay in the normal maturational decline; there was a parallel decrease in the glial/neuronal ratio. In the striatum, the number of neurons per unit area was reduced in the CPF group, accompanied by perikaryal hypertrophy, as evidenced by an increase in the average neuronal cell diameter. In the somatosensory cortex, the distribution of cell sizes indicated a decrease in the proportion of small, nonpyramidal cells. Thus, there are subtle morphological changes in the juvenile rat brain after neonatal CPF exposure that are detectable with quantitative analysis and that correlate with later emergence of behavioral alterations. Furthermore, the current findings support the hypothesis that CPF interferes with gliogenesis, a relatively late event in brain development; accordingly, the vulnerable period for adverse effects of CPF is likely to extend into childhood or adolescence.
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Affiliation(s)
- Tara Sankar Roy
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Box 3813 DUMC, Durham, NC 27710, USA
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90
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Qiao D, Seidler FJ, Abreu-Villaça Y, Tate CA, Cousins MM, Slotkin TA. Chlorpyrifos exposure during neurulation: cholinergic synaptic dysfunction and cellular alterations in brain regions at adolescence and adulthood. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2004; 148:43-52. [PMID: 14757517 DOI: 10.1016/j.devbrainres.2003.10.004] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The developmental neurotoxicity of chlorpyrifos (CPF) involves multiple mechanisms, thus rendering the immature brain susceptible to adverse effects over a wide window of vulnerability. Earlier work indicated that CPF exposure at the neural tube stage elicits apoptosis and disrupts mitotic patterns in the brain primordium but that rapid recovery ensues before birth. In the current study, we assessed whether defects in cholinergic synaptic activity emerge later in development. CPF was given to pregnant rats on gestational days 9-12, using regimens devoid of overt maternal or fetal toxicity. We then examined subsequent development of acetylcholine systems and compared the effects to those on general biomarkers of cell development. Choline acetyltransferase (ChAT), a constitutive marker for cholinergic nerve terminals, was increased in the hippocampus and striatum in adolescence and adulthood. In contrast, hemicholinium-3 (HC-3) binding to the presynaptic choline transporter, an index of nerve impulse activity, was markedly subnormal. Furthermore, m2-muscarinic cholinergic receptor binding was significantly reduced, instead of showing the expected compensatory upregulation for reduced neural input. CPF also elicited delayed-onset alterations in biomarkers of cell packing density, cell number, cell size and neuritic projections, involving brain regions both with and without reductions in indices of cholinergic activity. In combination with earlier results, the current findings indicate that the developing brain, and especially the hippocampus, is adversely affected by CPF regardless of whether exposure occurs early or late in brain development, and that defects emerge in adolescence or adulthood even in situations where normative values are initially restored in the immediate post-exposure period.
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Affiliation(s)
- Dan Qiao
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Box 3813 DUMC Rm c162, LSRC Building Research Drive, Durham, NC 27710, USA
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91
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Aldridge JE, Gibbons JA, Flaherty MM, Kreider ML, Romano JA, Levin ED. Heterogeneity of toxicant response: sources of human variability. Toxicol Sci 2003; 76:3-20. [PMID: 12883075 DOI: 10.1093/toxsci/kfg204] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
While risk assessment models attempt to predict human risk to toxicant exposure, in many cases these models cannot account for the wide variety of human responses. This review addresses several primary sources of heterogeneity that may affect individual responses to drug or toxicant exposure. Consideration was given to genetic polymorphisms, age-related factors during development and senescence, gender differences associated with hormonal function, and preexisting diseases influenced by toxicant exposure. These selected examples demonstrate the need for additional steps in risk assessment that are needed to more accurately predict human responses to toxicants and drugs.
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Affiliation(s)
- Justin E Aldridge
- Integrated Toxicology Program, Duke University Medical Center, Durham, North Carolina 27710, USA
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92
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Qiao D, Nikitina LA, Buznikov GA, Lauder JM, Seidler FJ, Slotkin TA. The sea urchin embryo as a model for mammalian developmental neurotoxicity: ontogenesis of the high-affinity choline transporter and its role in cholinergic trophic activity. ENVIRONMENTAL HEALTH PERSPECTIVES 2003; 111:1730-5. [PMID: 14594623 PMCID: PMC1241715 DOI: 10.1289/ehp.6429] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Embryonic development in the sea urchin requires trophic actions of the same neurotransmitters that participate in mammalian brain assembly. We evaluated the development of the high-affinity choline transporter, which controls acetylcholine synthesis. A variety of developmental neurotoxicants affect this transporter in mammalian brain. [3H]Hemicholinium-3 binding to the transporter was found in the cell membrane fraction at stages from the unfertilized egg to pluteus, with a binding affinity comparable with that seen in mammalian brain. Over the course of development, the concentration of transporter sites rose more than 3-fold, achieving concentrations comparable with those of cholinergically enriched mammalian brain regions. Dimethylaminoethanol (DMAE), a competitive inhibitor of choline transport, elicited dysmorphology beginning at the mid-blastula stage, with anomalies beginning progressively later as the concentration of DMAE was lowered. Pretreatment, cotreatment, or delayed treatment with acetylcholine or choline prevented the adverse effects of DMAE. Because acetylcholine was protective at a lower threshold, the DMAE-induced defects were most likely mediated by its effects on acetylcholine synthesis. Transient removal of the hyaline layer enabled a charged transport inhibitor, hemicholinium-3, to penetrate sufficiently to elicit similar anomalies, which were again prevented by acetylcholine or choline. These results indicate that the developing sea urchin possesses a high-affinity choline transporter analogous to that found in the mammalian brain, and, as in mammals, the functioning of this transporter plays a key role in the developmental, trophic activity of acetylcholine. The sea urchin model may thus be useful in high-throughput screening of suspected developmental neurotoxicants.
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Affiliation(s)
- Dan Qiao
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710-3813, USA
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93
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Slotkin TA, Seidler FJ, Yanai J. Heroin neuroteratogenicity: delayed-onset deficits in catecholaminergic synaptic activity. Brain Res 2003; 984:189-97. [PMID: 12932853 DOI: 10.1016/s0006-8993(03)03152-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Prenatal heroin exposure evokes neurochemical and behavioral deficits that, in part, reflect disruption of septohippocampal cholinergic function. In earlier studies, we found that cholinergic synaptic defects involve primary changes in cell signaling proteins that are shared by other transmitter systems. In the current study, we determined whether heroin also targets noradrenergic and dopaminergic inputs that operate through the same signaling cascades. Mice exposed to prenatal heroin showed significant deficits in norepinephrine and dopamine levels and much more pronounced effects on neurotransmitter turnover, an index of synaptic activity. Adverse effects were not present in the immediate postnatal period but rather emerged just before weaning and worsened subsequently. By young adulthood, the most highly-affected regions (hippocampus, cerebral cortex) displayed almost complete inactivation of noradrenergic and dopaminergic tonic activity. These effects arise after prior deficits in cell signaling are discernible, suggesting that the presynaptic effects are secondary to actions on signal transduction cascades shared by numerous neurotransmitter inputs and targeted by other neuroteratogens. These results may explain why apparently unrelated developmental neurotoxicants may ultimately produce a common set of neurochemical and behavioral anomalies.
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Affiliation(s)
- Theodore A Slotkin
- Department of Pharmacology and Cancer Biology, Box 3813 DUMC, Duke University Medical Center, Durham, NC 27710, USA.
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94
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Ricceri L, Markina N, Valanzano A, Fortuna S, Cometa MF, Meneguz A, Calamandrei G. Developmental exposure to chlorpyrifos alters reactivity to environmental and social cues in adolescent mice. Toxicol Appl Pharmacol 2003; 191:189-201. [PMID: 13678652 DOI: 10.1016/s0041-008x(03)00229-1] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Neonatal mice were treated daily on postnatal days (pnds) 1 through 4 or 11 through 14 with the organophosphate pesticide chlorpyrifos (CPF), at doses (1 or 3 mg/kg) that do not evoke systemic toxicity. Brain acetylcholinesterase (AChE) activity was evaluated within 24 h from termination of treatments. Pups treated on pnds 1-4 underwent ultrasonic vocalization tests (pnds 5, 8, and 11) and a homing test (orientation to home nest material, pnd 10). Pups in both treatment schedules were then assessed for locomotor activity (pnd 25), novelty-seeking response (pnd 35), social interactions with an unfamiliar conspecific (pnd 45), and passive avoidance learning (pnd 60). AChE activity was reduced by 25% after CPF 1-4 but not after CPF 11-14 treatment. CPF selectively affected only the G(4) (tetramer) molecular isoform of AChE. Behavioral analysis showed that early CPF treatment failed to affect neonatal behaviors. Locomotor activity on pnd 25 was increased in 11-14 CPF-treated mice at both doses, and CPF-treated animals in both treatment schedules were more active when exposed to environmental novelty in the novelty-seeking test. All CPF-treated mice displayed more agonistic responses, and such effect was more marked in male mice exposed to the low CPF dose on pnds 11-14. Passive avoidance learning was not affected by CPF. These data indicate that developmental exposure to CPF induces long-term behavioral alterations in the mouse species and support the involvement of neural systems in addition to the cholinergic system in the delayed behavioral toxicity of CPF.
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Affiliation(s)
- Laura Ricceri
- Laboratorio di Fisiopatologia, Istituto Superiore di Sanità, Rome, Italy.
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95
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Richardson J, Chambers J. Effects of gestational exposure to chlorpyrifos on postnatal central and peripheral cholinergic neurochemistry. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2003; 66:275-289. [PMID: 12521672 DOI: 10.1080/15287390306369] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The effects of gestational exposure to the commonly used organophosphorus insecticide chlorpyrifos (O,O-diethyl O-[3,5,6-trichloro-2-pyridinyl]phosphorothioate) on postnatal central and peripheral cholinergic neurochemistry were investigated. Pregnant rats were orally dosed daily with chlorpyrifos (0, 3, 5, or 7 mg/kg) in corn oil from gestation day 6 to 20. Pups were sacrificed on postnatal days 1, 3, 6, 9, and 12 for the determination of brain, heart, lung, and serum cholinesterase, and brain choline acetyltransferase activities, along with liver carboxylesterase activity. Exposure to chlorpyrifos did not produce signs of overt toxicity to the dams or developing offspring. Cholinesterase activities were inhibited in a dose-related manner, with brain cholin-esterase inhibition of about 26%, 32%, and 45% on postnatal day 1. Inhibition of brain cholineste-rase persisted in all treatment groups until postnatal day 6 and in the medium and high-dosage groups through postnatal day 9. Liver carboxylesterase activity was also inhibited in a dose-related manner, with a recovery profile parallel to that of brain cholinesterase. Choline acetyltransferase activity was decreased by about 13% in the high-dosage group on postnatal days 9 and 12. These results indicate that gestational exposure to chlorpyrifos results in relatively persistent inhibition of brain cholinesterase and a delayed depression of choline acetyltransferase at a time when brain cholinesterase activity had returned to control levels in the high-dosage group.
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Affiliation(s)
- Jason Richardson
- Center for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi 39762-6100, USA
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96
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Dam K, Seidler FJ, Slotkin TA. Transcriptional biomarkers distinguish between vulnerable periods for developmental neurotoxicity of chlorpyrifos: Implications for toxicogenomics. Brain Res Bull 2003; 59:261-5. [PMID: 12464398 DOI: 10.1016/s0361-9230(02)00874-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The widespread use of organophosphate insecticides has raised concern about neurotoxic effects of fetal and childhood exposures. Studies in rats show that chlorpyrifos (CPF) elicits CNS cell damage, in part, through noncholinergic mechanisms that involve alterations in the expression and function of nuclear transcription factors that control cell replication, differentiation, and apoptosis. In the current study, we examined mRNAs encoding c-fos and p53, in order to determine if changes in these factors correspond to the differential susceptibility of forebrain neurons and glia, when exposure is shifted from the early neonatal period (postnatal days 1-4) to a later period (days 11-14). The early treatment paradigm elicited a significant elevation of c-fos whereas the later treatment suppressed c-fos. Neither regimen altered forebrain p53 expression, but values were elevated in the cerebellum following the later treatment; the cerebellum develops later than the forebrain and has its peak of neurogenesis postnatally. Our results suggest that a wider profiling of mRNAs using genomic arrays would enable screening for developmental neurotoxicants, but that regional and temporal profiles will be required in order to draw mechanistic conclusions or to identify critical periods of vulnerability.
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Affiliation(s)
- Kristina Dam
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
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97
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Levin ED, Chrysanthis E, Yacisin K, Linney E. Chlorpyrifos exposure of developing zebrafish: effects on survival and long-term effects on response latency and spatial discrimination. Neurotoxicol Teratol 2003; 25:51-7. [PMID: 12633736 DOI: 10.1016/s0892-0362(02)00322-7] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chlorpyrifos (CPF) is a widely used insecticide, which has been shown to interfere with neurobehavioral development. Rat models have been key in demonstrating that prenatal CPF exposure causes choice accuracy deficits and motor alterations, which persist into adulthood. Complementary nonmammalian models can be useful in determining the molecular mechanisms underlying the persisting behavioral effects of developmental CPF exposure. Zebrafish with their clear chorion and extensive developmental information base provide an excellent model for assessment of molecular processes of toxicant impacted neurodevelopment. To facilitate the use of the zebrafish model and to compare it to the more typical rodent models, the behavioral phenotype of CPF toxicity in zebrafish must be well characterized. Our laboratory has developed methods for assessing spatial discrimination learning in zebrafish, which can differentiate response latency from choice accuracy in a three chambered fish tank. Low and high doses of CPF (10 and 100 ng/ml on days 1-5 postfertilization) both had significant persisting effects on both spatial discrimination and response latency over 18 weeks of testing. The high, but not the low dose, significantly accelerated mortality rates of the fish during the study from 20-38 weeks of age. Developmental exposure to either 10 or 100 ng/ml of CPF caused significant spatial discrimination impairments in zebrafish when they were adults. The impairment caused by 10 ng/ml was seen during early but not later testing, while the impairment caused by 100 ng/ml became more pronounced with continued testing. The higher dose caused a more pervasive impairment. The 10 and 100 ng/ml doses had opposite effects on response latency. The low 10 ng/ml dose significantly slowed response latency, while the high 100 ng/ml dose significant increased response latency. Both of these effects diminished with continued testing. CPF exposure during early development caused clear behavioral impairments, which lasted throughout adulthood in zebrafish. The molecular mechanisms by which early developmental CPF exposure produces these behavioral impairments expressed in adulthood can now be studied in the zebrafish model.
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Affiliation(s)
- Edward D Levin
- Department of Psychiatry and Behavioral Sciences, Box #3412, Duke University Medical Center, Durham, NC 27710, USA.
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98
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Levin ED, Addy N, Baruah A, Elias A, Christopher NC, Seidler FJ, Slotkin TA. Prenatal chlorpyrifos exposure in rats causes persistent behavioral alterations. Neurotoxicol Teratol 2002; 24:733-41. [PMID: 12460655 DOI: 10.1016/s0892-0362(02)00272-6] [Citation(s) in RCA: 168] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Use of chlorpyrifos (CPF) has been curtailed due to its developmental neurotoxicity. In rats, postnatal CPF administration produces lasting changes in cognitive performance, but less information is available about the effects of prenatal exposure. We administered CPF to pregnant rats on gestational days (GD) 17-20, a peak period of neurogenesis, using doses (1 or 5 mg/kg/day) below the threshold for fetal growth impairment. We then evaluated performance in the T-maze, Figure-8 apparatus and 16-arm radial maze, beginning in adolescence and continuing into adulthood. CPF elicited initial locomotor hyperactivity in the T-maze. Females showed slower habituation in the Fig. 8 maze; no effects were seen in males. In the radial-arm maze, females showed impaired choice accuracy for both working and reference memory and again, males were unaffected. Despite the deficits, all animals eventually learned the maze with continued training. At that point, we challenged them with the muscarinic antagonist, scopolamine, to determine the dependence of behavioral performance on cholinergic function. Whereas control females showed impairment with scopolamine, CPF-exposed females did not, implying that the delayed acquisition of the task had been accomplished through alternative mechanisms. The differences were specific to muscarinic circuits, as control and CPF groups responded similarly to the nicotinic antagonist, mecamylamine. Surprisingly, adverse effects of CPF were greater in the group receiving 1 mg/kg as compared to 5 mg/kg. Promotional effects of acetylcholine (ACh) on cell differentiation may thus help to offset CPF-induced developmental damage that occurs through other noncholinergic mechanisms. Our results indicate that late prenatal exposure to CPF induces long-term changes in cognitive performance that are distinctly gender-selective. Additional defects may be revealed by similar strategies that subject the animals to acute challenges, thus, uncovering the adaptive mechanisms that maintain basal performance.
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Affiliation(s)
- Edward D Levin
- Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC 27710, USA.
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99
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Karaoz E, Gultekin F, Akdogan M, Oncu M, Gokcimen A. Protective role of melatonin and a combination of vitamin C and vitamin E on lung toxicity induced by chlorpyrifos-ethyl in rats. EXPERIMENTAL AND TOXICOLOGIC PATHOLOGY : OFFICIAL JOURNAL OF THE GESELLSCHAFT FUR TOXIKOLOGISCHE PATHOLOGIE 2002; 54:97-108. [PMID: 12211644 DOI: 10.1078/0940-2993-00236] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The ameliorating effects of melatonin and vitamin C plus vitamin E were examined histologically and biochemically in lung tissues in rats exposed to chlorpyriphos-ethyl (CE). Experimental groups were as follows: Control group (C), CE treated group (CE), vitamin C plus vitamin E treated group (Vit), melatonin treated group (Mel), vitamin C plus vitamin E plus CE treated group (Vit + CE), and melatonin plus CE treated group (Mel + CE). Vitamin E and vitamin C were administered intramuscularly at the rates of 150 and 200 mg per kg body weight, respectively, in Vit and Vit + CE groups, once a day for 6 consecutive days. Melatonin was administered intramuscularly at the rate of 10 mg per kg body weight in Mel and Mel + CE groups, once a day for 6 consecutive days. At the end of the fifth day, the rats of CE, Vit + CE and Mel + CE groups were treated orally with CE dissolved in corn oil with two equal doses of 41 mg CE per kg body weight at zero and twenty-first hours. Tissue samples of lungs were taken by using appropriate techniques for biochemical and histological examinations under anesthesia at the twenty-fourth hours of CE administration, at the end of the sixth day of the experiment. In tissue homogenates, the level of thiobarbituric acid reactive substances (TBARS), antioxidant potential (AOP), and the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) were determined. TBARS was significantly high (p < 0.05) in CE group compared to control group, while TBARS was found to significantly decrease (p < 0.05) with Vit and Mel groups compared to control. On the other hand, TBARS was seen to significantly decrease (p < 0.05) in both groups of Vit + CE and Mel + CE compared to CE group. In comparison with CE group, SOD activity was significantly high (p < 0.05) with the groups of Vit, Mel, Vit + CE and Mel + CE. GSH-Px activity was found to significantly decrease (p < 0.05) with CE group, compared with both C and Vit groups. AOP was significantly lower (p < 0.01) in CE group than C group. Although there was an increased AOP with Vit + CE and Mel + CE groups compared to CE group, the increase in AOP was only seen to be significant (p < 0.05) in Mel + CE group. In comparison with C group, AOP significantly (p < 0.05) increased with Vit group. There was also a significant (p < 0.05) increase in AOP with Mel + CE group, compared with CE group. Additionally, AOP was significantly lower (p < 0.05) in Vit + CE group than Mel + CE group. Lungs were examined histologically at the end of sixth day. There were remarkable changes in the histomorphology of peribronchial and perivascular area in the lung of rats treated with CE. These were infiltration of mononuclear cells (such as lymphocytes, plasmocytes, macrophages), hyperplasia of type II pneumocyte, and thickened and increased connective tissue. Damage to the lung tissue such as increased inflammatory mononuclear cells in peribronchial and perivascular areas were more pronounced for the CE group than Vit + CE and Mel + CE groups in which these changes were higher than C, Vit and Mel groups. These results suggest that CE increases lipid peroxidation and decreases antioxidant enzymes activities and AOP due to increasing oxidative stress induced by CE, and high doses of vitamin C plus vitamin E and melatonin considerably reduce CE toxicity in lung tissues of rats.
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Affiliation(s)
- Erdal Karaoz
- Suleyman Demirel University, Faculty of Medicine, Department of Histology, Isparta, Turkey
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100
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Gore AC. Organochlorine pesticides directly regulate gonadotropin-releasing hormone gene expression and biosynthesis in the GT1-7 hypothalamic cell line. Mol Cell Endocrinol 2002; 192:157-70. [PMID: 12088877 DOI: 10.1016/s0303-7207(02)00010-2] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Environmental toxicants profoundly affect growth and developmental processes. In the present study, we hypothesized that hypothalamic gonadotropin-releasing hormone (GnRH) neurons, which regulate the reproductive axis, are targets of environmental endocrine disrupting chemicals. Two organochlorine pesticides (methoxychlor and chlorpyrifos) were tested for their effects on GnRH gene expression and biosynthesis in the immortalized hypothalamic GT1-7 cells, which synthesize and secrete GnRH. GT1-7 cells were treated with methoxychlor or chlorpyrifos for 24 h in dose-response experiments, and GnRH gene expression and peptide levels were quantified. In order to examine whether these pesticides affect GnRH biosynthesis through the estrogen receptor (ER), in other experiments their effects were compared to those of estrogen, or they were co-administered with the ER antagonist, ICI 182,780 (ICI). Both methoxychlor and chlorpyrifos had significant effects on GnRH gene transcription and GnRH mRNA levels. These effects were not consistently blocked by ICI, nor did the effects of these pesticides consistently mimic those of estrogen, suggesting a mechanism independent of the ER. Chlorpyrifos and methoxychlor slightly stimulated peptide levels, and this effect was blocked by ICI, suggesting that the ER may mediate effects of pesticides on GnRH release. These results indicate that chlorpyrifos and methoxychlor alter GnRH biosynthesis in this hypothalamic cell line in vitro, suggesting that they may have endocrine disrupting effects on GnRH neurons in vivo.
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Affiliation(s)
- Andrea C Gore
- Kastor Neurobiology of Aging Laboratories, Fishberg Research Center for Neurobiology, and Brookdale Department of Geriatrics and Adult Development, Mount Sinai School of Medicine, Box 1639, New York, NY 10029, USA.
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